Ignition system



Jan. 1, 1946. w. E. SARGEANT IGNITION SYSTEM Filed Aug. 8, 1941 2 Sheets-Sheet 1 gfzs 0 C. SOURCE Enventor m m m PLATE GIIPC'U/T'CUIPIPE/VT Jan. 1, 1946. w SARGEANT V 2,392,066

IGNITION SYSTEM Filed Aug; 8, 1941 2 Sheets-Sheet 2 g A TIME 5 A 77ME C 5 v r J 1 4 in/Z62 ifa'gc' z g r #00 W V- l Cfltomegs Patented Jan. I, 1946 umreo STATES PATENT OFFICE IGNITION SYSTEM Walter E. Sargeant, Ferndale, Micln, asslgnor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application August 8, 1941, Serial No. 405,952

11 Claims..

- My invention relates to ignition systems of the tems. Considerable difflculty has also been experienced in securing interrupter points which would stand up under the severe arcing existing in present ignition systems.

It is the object of my invention to overcome the aforesaid disadvantages of existing ignition systems by utilizing an electric valve, such as a grid controlled vacuum tube, to break the primary circuit of the transformer. A contactor is used to control the grid circuit. The grid circuit is always a low ampere circuit and there is little wear on the contactor points because of the decreased tendency to arc.

Figure 1 of the accompanying drawings is a circuit diagram of an ignition system embodying my invention.

Figures 2, 3 and 4 are graphs in which plotted against plate circuit current, plate voltage, and grid voltage, respectively, for one complete ignition cycle.

time is o In the ignition system shown in the drawings 4 indicates a suitable source of electrical energy. Where the energy source is an ordinary 6-volt battery, I have found it necessary to use means to increase the voltage, such as a converter. Numerous converters are available which might serve the purpose of my system. I have found that a D. C. supply of 110 volts gives satisfactory operation.

V A transformer is designated generally'by 6. This transformer has primary and secondary i windings 8 and II) respectively. An electric valve source is connected to the other primary coil.

anodes l4 are connected directly to one terminal of the primary winding 8 and the cathodes it are connected to the negative side of the principal power source. The positive lead from this power al of the A battery it! is provided to heat the cathodes l6.

Control grids 20 are connected with an auxiliary primary winding 22. An interrupter or contactor 24 connects coil 22 with the positive side of the principal power source. A resistor 26 in this circuit serves to keep current flow through the grid circuit low as compared to the plate circult.

Also connected to auxiliary coil 22 is a source of negative voltage such as battery 28. Battery 28 is connected to coil 22 through a filter circuit comprising resistance 30 and capacitance 32. By incorporating auxiliary winding 22 in my ignition system, I have found a negative bias of 22 or 23 volts satisfactory.

Secondary winding I0 is connected to a distributor 34 from which suitable leads or conductors go out to spark plugs 36. I have illustrated four plugs connected to a four-point distributor such as would be used in a four cylinder engine. In practice, of course, these plugs would The inductances, resistances, and capacities necessary to an operative ignition system embodyme my invention are not critical. I have found that the following values give satisfactory performance: for winding 8 of the transformer, 1700 turns of No. 21 wire having an inductance of .6 henry and a resistance of approximately 14 ohms; for winding III of the transformer, 17,000 turns of No. 38 wire having an inductance of henrys and a resistance of approximately 2500 ohms; and for winding 22, 200 turns of No. 30 wire having .01 henry inductance, and approximately 10 ohms resistance. Resistance 26 should have a value in the vicinity of 1000 ohms. Resistance 30 should have a value of approximately 5000 ohms. Condenser 32 should have a capacity of approximately .01 microfarad. The operation of my ignition system is as follows: With the contacts of interrupter 24 closed, a positive voltage bias is applied to control grids 20 which serves to make the tubes l2 conductive. A current builds up slowly through primary windings 8 and 22 so that there is insufllcient rate of change in the magnetic field established by these primary windings to cause sparking of any of'the plugs. At

the appropriate point in the cycle, which is determined by a suitable timing mechanism, the contact points of interrupter 24 are opened. Control grids 20 are thereby disconnected from the positive side of the principal power source, and are immediately effectively connected to the negative side of battery 28. The positive voltage applied to coil 22 is therefore rapidly reversed. Viewed in greater detail, it is seen that a small increment of change in voltage from positive to negative on the grid causes a change in the flux of winding 22, and therefore 'transformer 6, which necessarily affects winding 8. The resulting change in flux in winding 8, operating through the flux-linkage of transformer 6, afl'ects winding 22 to still further decrease the voltage on winding 22 and to still further collapse the field. This "feed-back characteristic results in a rapid reduction of the voltage on grids 20. In fact, because of the feed-back, a voltage surge occurs which is considerably greater inmagnitude than the voltage of battery 28. It is this feed-back characteristic which makes it possible to use a battery of rather small potential at this point in the system.

The previously described collapse of the magnetic field in the primary windin s induces a large voltage in secondary winding III, which causes a spark to jump across the gap of the spark plug in the distributor circuit at that time.

What happens in the tube circuits of my ignition system is perhaps best indicated in Figures 2, 3 and 4. In these figures, time is plotted as abscissa and plate circuit current, plate voltage and grid voltagefrespectively, are the ordinates. The time interval AB represents a complete ignition cycle. This time interval necessarily varies with variation in the engine speed.

At point C, between A and B, the contact points of interrupter 24 are opened. The application thereupon of the negative voltage of battery 28 initiates a negative potential surge of approximately 100 volts, by virtue of the feed-back characteristics of windings 8 and 22 previously described. This is indicated in Figure-4. This negative potential surge serves to block the flow. of electrons to the plate. When the plate current is thus reduced to a negligible flow. the collapse of the field of transformer 8 induces a voltage in secondary winding I which causes a spark to jump the gap of the plug selected by the distributor.

With my ignition system, I find it possible to et much more accurate timing than with ignition systems commonly in use today due to the elimination of arcing and the use of lighter contacts permitted in my system. It may be found desirable to substitute a trip device on the flywheel for the contactor, thereby eliminating gears with their associated lash and lost motion. This trip device may be magnetically or optically controlled, as desired.

A further advantage of my ignition system is that the current flowing through the contacts of the interrupter is so small that very little damage series circuit relation with the secondary winding, a source of electrical energy connected to one terminal of the primary winding, 9. three-electrode electric valve, an electrical connection from the other terminal of the primary winding to the anode of the valve, another electrical connection from the cathode of the electric valve to the energy source, a circuit interrupter connected to the energy source, an electrical connection from the circuit interrupter to the control grid of the electric valve applying a potential of a given polarity to the grid, and a source of electrical potential of the opposite polarity connected to the control grid circuit.

2. In combination, a transformer having primary and secondary windings, a spark gap in series circuit relation with the secondary winding, a source of electrical energy connected to one terminal of the primary winding, a three-electrode electric valve, an electrical connection from the other terminal of the primary windingto the anode of the valve, another electrical connection from the cathode of the electric valve to the energy source, a circuit interrupter connected to the energy source, an auxiliary primary coil connected to the circuit interrupter, an electrical connection from the auxiliary coil to the control grid of the electric valve to apply a potential of a given polarity to said grid, and a source of electrical potential of the opposite polarity connected to the control grid circuit.

3. An ignition system for internal combustion engines comprising a transformer having primary and secondary windings, a source of electric power connected to one terminal of the primary winding, a grid controlled vacuum tube, a connection from the other terminal of the primary winding to the anode of the tube, a connection from the cathode of the tube to the power source, a circuit interrupter connected to the power source, an auxiliary coil connected to the circuit interrupter, an electrical connection from the auxiliary coil to the control grid completing a control grid circuit in which a potential of one polarity is applied to the grid, and a source of electrical potential of the opposite polarit connected to the grid circuit.

4. In combination, a transformer having primary and secondary windings; a spark gap in series circuit relation with the secondary winding; a source of electrical energy connected to one terminal of the primary winding; a-grid controlled vacuum tube; a connection from the other terminal of the primary winding to the anode of the tube; a connection from the cathode of the tube to the energy source; means for heating the tube cathode; a control circuit for the vacuum tube comprising the aforesaid energy source, a resistance connected to said in the way of pitting and the like results to the source, a circuit interrupter connected to the resistance, an auxiliary primary coil connected to the circuit interrupter, a connection from the auxiliary coil to the control grid, and means for applying a control potential to the control grid upon opening of the circuit by the circuit interrupter whereb opening of the circuit interrugter makes the tube non-conductive causing collapse of the transformer field thereby inducing a voltage in the secondar winding which causes a spark to jump across the spark gap.

5. In combination, a transformer having primary and secondary windings, aspark gap in series circuit relation with the secondary winding, a source of electrical energy connected to .supply energy to the primary winding 0';

, lary being magnetically coupled with the transformer.

asaaoce transformer, a grid controlled electric valve connected in the circuit including the energy source and the primary winding, a source or potential of one polarity for the grid of said electric valve, a source of potential or the opposite polarity for said grid, and means operating in timed relation with the requirements or the secondary winding for disconnecting the first source of grid potential.

--6.*The combination of claim 5, and means in the grid circuit for accelerating the reversal of polarity of the grid.

'7. The combination of claim 5, and an auxilwinding in said grid circuit, said winding ing primary and secondary windings, an electricpower source connected'to the primary winding, a spark gap connected to the secondary windmg, electronic means in the power source connection to the primary winding to normally admit passage or electric current from the power source to the primary winding, control means for said last-mentioned means to permit blocking said current passage. in timed relation with the requirements of the secondary winding circuit, and an auxiliarywinding for said trans- I former connected to said control means.

10; An ignition system for internal combustion engines comprising a transformer having a primary and a secondary winding, a spark gap in series with the secondary, a source 01 electric power, an electronic tube having two main and one control electrodes, a series circuit connecting the source or power and the transformer primary to the two mainelectrodes of the tube,

a separate biasing voltage and means connectins both the biasing voltage and the power source to the control electrode.

11. An ignition system for internal combustion engines comprising a transformer having a primary and a secondary winding, a spark gap in series with the secondary, 'a source of electric power. an electronic tube having two main and one control electrodes, a series circuit connecting thevsource or power and the transformer primary to the two main electrodes of the tube, a separate biasing voltage, means connecting both the biasing voltage and the power source to the control electrode and timing means connected to interrupt the connection of the power source to the control electrode.

. WALTER E. SaRGEANT. 

